Delay-dependent robust stability and H_∞ analysis of stochastic systems with time-varying delay

This paper investigates the robust stochastic stability and H∞ analysis for stochastic systems with time-varying delay and Markovian jump. By using the freeweighting matrix technique, i.e., He's technique, and a stochastic Lyapunov-Krasovskii functional, new delay-dependent criteria in terms of linear matrix inequalities are derived for the the robust stochastic stability and the H∞ disturbance attenuation. Three numerical examples are given. The results show that the proposed method is efficient and much less conservative than the existing results in the literature.     

大庆油田三元复合驱结垢样品中碳酸钙的结晶特性及形貌特征

采用EDAX, XRD和SEM等方法对大庆油田三元复合驱结垢样品中碳酸钙的结晶特性及形貌特征进行了研究. 结果表明, 结垢样品中的碳酸钙呈现出球形、棒状和花状等形貌特征和层状生长的结晶特征. 部分水解聚丙烯酰胺(HPAM)降低了重烷基苯磺酸盐(HABS)表面活性剂的临界胶束浓度(cmc), 促进了其胶束化作用; HABS使溶液中HPAM链的刚性增强, 负电吸引能力增强; 二者均会形成模板, 导致结垢样品中的碳酸钙具有不同的形貌特征. 聚丙烯酰胺和表面活性剂的存在未改变结垢样品中碳酸钙的层状生长特征.     

电场诱导二氧化钒绝缘-金属相变的研究进展

二氧化钒(VO_2)是电子强关联体系的典型代表,其晶体结构在特定阈值的温度、电场、光照和压力等物理场作用下会发生由单斜金红石结构向四方金红石结构的可逆转变,从而引发绝缘-金属相变.其中,电场诱导VO_2绝缘-金属相变后的电导率可提高2-5个数量级,在可重构缝隙天线、太赫兹辐射以及智能电磁防护材料等领域具有广阔的应用前景,成为近年来人们的研究热点.首先,简要概述了VO_2发生绝缘-金属相变时晶体结构和能带结构的变化,进而从电场诱导VO_2绝缘-金属相变的研究方法、响应时间、临界阈值场强调控以及相变机理几个方面系统总结和评述了近年来国内外学者在该领域的重要发现和研究进展.最后,指出了当前VO_2绝缘-金属相变研究存在的问题,并展望了未来的发展方向.     

略谈电子对抗技术及其物理基础

介绍电子对抗技术的基本概念，并从电磁波的传播特性，电磁波与物质的相互作用两个方面，综述了电子对抗技术的物理原理及其最新发展。     

Growth and spectroscopic characteristics of Nd-doped PbWO₄ crystal

Nd-doped PbWO4 crystals are grown by using the modified Bridgman method.The spectroscopic properties of the crystals are investigated.The changes of the absorption band at 350 nm are discussed for samples annealed at 740℃ and 1040℃.The radiative lifetime of the 4 F 3/2 level is calculated by using the Judd-Ofelt theory according to the absorption spectrum of 0.5 at.% Nd-doped PbWO 4 crystal.The spontaneous Raman scattering properties of the crystals are analysed.     

红色Bi4 Ge3 O12晶体在低温下的发光性能

用下降法制备了Bi₄Ge₃O₁₂晶体,发现生长出来的圆柱状晶体外侧呈现淡红色。对红色Bi₄Ge₃O₁₂晶体进行了低温(至8 K)下的近红外发射光谱及衰减寿命等测试分析。发现低温时(200 K以下)红色Bi₄Ge₃O₁₂在1 150 nm等波长处有较强的发射峰,强度随温度降低而增强,衰减时间为几百μs。     

Spectroscopic properties of Er/Ce-codoped La3Ga5SiO14

The Er-single-doped and Er/Ce-codoped La₃Ga₅SiO₁₄ polycrystalline powders are synthesized by the solid-phase synthesis method. The room-temperature luminescence spectra of the samples are investigated. The Near-infrared-region spectroscopic properties of Er³⁺ ions in the La₃Ga₅SiO₁₄ systems are analysed with Judd-Ofelt theory and rate equations. The effective deactivating effect of Ce³⁺ ions on Er³⁺ ions is confirmed.     

点状籽晶法生长KDP晶体中散射颗粒分布

在不同的溶液pH值条件下进行了点状籽晶法慢速和快速生长KDP晶体实验,发展了观察晶体中散射颗粒分布的激光层析技术,通过图像处理得到了KDP晶体内部(100)面完整的散射颗粒分部图,对不同生长速度、不同pH值条件下点状籽晶法生长的KDP晶体的散射颗粒分部做了对比.利用表面光学投影技术观察了晶体表面宏观形貌,并由此分析了不同生长条件下生长机制对散射颗粒分布的影响.测定了散射颗粒密度不同部位的晶体透过率.